With the various types of pneumatic processing metallurgical vessels, for example BOF vessels, it is necessary to capture the hot exhaust gases generated during operation and to conduct these gases to exhaust devices remote from the vessel generating the hot gases. A common technique for capturing and conducting the exhaust gases is a hood system arrangement formed of hollow metal members which are joined together with one end of the system being open and overlying the portion of the metallurgical vessel from which hot gases are exiting. The hood system commonly comprises vertical, oblique and horizontal portions in order to conform to space restrictions and consequently the exposure to hot exhaust gases varies from location to location in the hood system. Hood systems are currently cooled in order to avoid failure due to exposure to hot exhaust gases typically through the use of water cooled elements, e.g. plates, in which water is continuously circulated through a circuit of closed conduits. The achievement of effective and efficient cooling is complicated due to the wide variety of temperature conditions in different portions of the hood system and the extent and irregular configuration of hood systems and the use of cooling arrangements which apply the same cooling system to different portions of the hood assembly results in serious inefficiencies. It is also known to spray cool roofs and sidewalls of metallurgical vessels using substantially uniformly arranged spray nozzles which overlay the entire roof or sidewall and being supplied with coolant from a common source.